Method for generating rights object and device to perform the method, method for transmitting rights object and device to perform the method, and method for receiving rights object and device to perform the method

ABSTRACT

A method for transmitting a Rights Object (RO) includes generating a password key by encrypting a password, generating the RO using the password key, and transmitting the RO from a first device to a second device. The second device and the first device share the password and the second device generates the password key using the same encryption method as that used by the first device to generate the password key. The second device decrypts a Message Authentication Code (MAC) key and a Rights Object Encryption Key (REK) using the password key, decrypts a Content Encryption Key (CEK) using the decrypted REK, and verifies integrity of the RO using the decrypted MAC key. The second device can use and/or access content associated with the RO using the decrypted CEK. The CEK may be generated by the first device or may be the CEK from a Rights Issuer.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication No. 10-2008-0027891, filed on Mar. 26, 2008, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a digital rights management technology and,more particularly, to a method for generating, transmitting, and/orreceiving a rights object (RO) as a part of digital rights management(DRM), and a device to perform one or more of the methods.

2. Discussion of the Background

Digital Rights Management (DRM) is a technology that protects andmanages the rights of copyright holders of digital contents. DRM mayinclude encryption, watermarking, and duplication preventiontechnologies.

Digital copyright data is encoded to DRM Content Format (DCF) digitalcontent using a Rights Object (RO) including coded digital content andcontent access rights information, prior to distribution. A RightsIssuer (RI) creates the RO and provides it to a device that will use theDRM content. Because digital copyright data is accessible only with anRO having a key with which to decode the digital copyright data, adevice that will use the DCF digital content should acquire the RO aswell.

SUMMARY OF THE INVENTION

This invention provides a method for generating an RO based on apassword, and a device to perform the method.

This invention also provides a method for transmitting an RO, and adevice to perform the method.

This invention also provides a method for receiving an RO, and a deviceto perform the method.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

This invention provides a method for generating an RO, includinggenerating a password key by encrypting a password, and generating theRO using the password key.

This invention also provides a device for generating an RO, including auser input portion to receive a password, and a controller to generate apassword key by encrypting the password, and to generate the RO usingthe password key.

This invention also provides a method for transmitting an RO, includinggenerating a password key by encrypting a password, generating the ROusing the password key, and transmitting the RO from a first device to asecond device.

This invention also provides a device for generating an RO, including auser input portion to receive a password, a controller to generate apassword key by encrypting the password, and to generate the RO usingthe password key, and a communication module to transmit the RO from thedevice to a receiving device.

This invention also provides a method for receiving an RO, includingreceiving the RO at a first device from a second device, generating apassword key by encrypting a password shared between the first deviceand the second device, and interpreting the RO using the password key.

This invention also provides a device for receiving an RO, including acommunication module to receive the RO from a transmitting device, astorage to store a password shared with the transmitting device, and acontroller to generate a password key by encrypting the password, and tointerpret the RO using the password key.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theaspects of the invention.

FIG. 1 illustrates a 4-pass registration protocol of Open MobileAlliance (OMA) DRM v.2.0.

FIG. 2 illustrates a 2-pass RO acquisition protocol of OMA DRM v.2.0.

FIG. 3 illustrates an RO transmission operation between devicesaccording to an exemplary embodiment of the present invention.

FIG. 4 illustrates an RO according to an exemplary embodiment of thepresent invention.

FIG. 5 illustrates a device for generating, transmitting, and/orreceiving an RO an RO according to an exemplary embodiment of thepresent invention.

FIG. 6 is a flowchart illustrating a method for generating andtransmitting an RO according to an exemplary embodiment of the presentinvention.

FIG. 7 is a flowchart illustrating a method for generating an ROaccording to an exemplary embodiment of the present invention.

FIG. 8 is a flowchart illustrating a method for receiving an ROaccording to an exemplary embodiment of the present invention.

FIG. 9 is a flowchart illustrating a method for interpreting an ROaccording to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The invention is described more fully hereinafter with reference to theaccompanying drawings, in which exemplary embodiments of the inventionare shown. This invention may, however, be embodied in many differentforms and should not be construed as limited to the exemplaryembodiments set forth herein. Rather, these exemplary embodiments areprovided so that this disclosure is thorough, and will fully convey thescope of the invention to those skilled in the art. In the drawings, thesize and relative sizes of layers and regions may be exaggerated forclarity. Like reference numerals in the drawings denote like elements.

If an element is referred to as being “connected to” another element, itcan be directly connected to the other element, or intervening elementsmay be present. In contrast, if an element is referred to as being“directly connected to” another element, there are no interveningelements present.

FIG. 1 illustrates a 4-pass registration protocol of Open MobileAlliance (OMA) DRM v.2.0.

According to OMA DRM v.2.0, a device registers with an RI by the 4-passregistration protocol to acquire an RO. The 4-pass registration protocolis used to exchange and register information for the device tocommunicate with the RI. If the 4-pass registration protocol issuccessful, the device acquires an RI context having information aboutthe RI, and the RI preserves information about the device.

To be more specific, the above operation starts with the device'stransmission of a Device Hello message carrying its basic information tothe RI in step S1. Upon receipt of the Device Hello message, the RItransmits an RI Hello message with the RI information to the device instep S2. Upon receipt of the RI Hello message, the device transmits aRegistration Request message to the RI, for registering with the RI instep S3.

In step S10, the RI transmits an Online Certificate Status Protocol(OCSP) Request message to an OCSP responder. The OCSP responder repliesto the RI with an OCSP Response message in step S11. The RI, which hasreceived the registration request, transmits a Registration Responsemessage including the OCSP Response message to the device in step S4.

FIG. 2 illustrates a 2-pass RO acquisition protocol of OMA DRM v.2.0.

Once the device has registered with the RI in the manner illustrated inFIG. 1, the device acquires an RO in the following procedure. First, thedevice transmits an RO Request message to the RI in step S20, and the RItransmits an OCSP Request message to the OCSP responder in step S30. Instep S31, the OCSP responder replies to the RI with an OCSP Responsemessage. The RI, which has received the RO Request message, generates anRO and transmits it in an RO Response message to the device in step S21.The RO is encrypted with a public key of the device to prevent otherdevices from using the RO.

As described above, only the RI can generate an RO according to OMA DRMv.2.0. However, the device can generate the RO and transmit it toanother device in accordance with an exemplary embodiment of the presentinvention.

A device is defined as a terminal capable of using digital content. Thedevice can be any type of terminal including, for example, a mobilecommunication terminal, a digital TV, a Global Positioning System (GPS)navigator, a portable game player, and a Moving Picture Experts GroupLayer 3 (MP3) player.

FIG. 3 illustrates an RO transmission operation between devicesaccording to an exemplary embodiment of the present invention.

According to the exemplary embodiment of the present invention, a devicecan generate an RO based on a user-entered password and transmit the ROto another device. The RO can be transmitted separately or together withdigital content associated with the RO in a DCF. Herein, theRO-transmitting device is referred to as a first device 100 and theRO-receiving device is referred to as a second device 200.

The first device 100 receives a password from the user in step S310 andgenerates a password key, which may have a predetermined length, usingthe password according to an encryption method in step S320. Forexample, the first device 100 receives a password of a predeterminedlength and a desired key length, and outputs a password key of thereceived key length by internal computation.

In accordance with the exemplary embodiment of the present invention,while the password key can be generated using a password-basedencryption method complying with Public-Key Cryptography Standard (PKCS)#5, any other encryption method can be used if it provides addedsecurity over non-encryption and if the key can be generated by theresources available in the device.

Then, the first device 100 generates an RO using the password key instep S330 and transmits the RO to the second device 200 in step S340.The RO can be transmitted using a hardwired connection, Infrared DataAssociation (IrDA), Multimedia Messaging System (MMS), Universal Plug &Play (UPnP), or another method of transferring data from the firstdevice 100 to the second device 200.

In step S350, after receiving the RO, the second device 200 interpretsthe RO and decrypts an encrypted Content Encryption Key (CEK) includedin the RO. According to the exemplary embodiment of the presentinvention, the second device 200 can receive the password input to thefirst device 100 and generate the password key by encrypting thepassword using the same encryption method as that used in the firstdevice 100. The second device 200 can then interpret the RO with thepassword key.

In step S360, the second device 200 can recover content by decryptingthe content using the decrypted CEK. The content can be receivedtogether with the RO from the first device 100 or can be content alreadystored in the second device 200.

FIG. 4 illustrates an RO according to an exemplary embodiment of thepresent invention.

In accordance with the exemplary embodiment of the present invention,the RO may include an <ro> element 410 with content of the RO and a<mac> element 420 with information for verifying the integrity of the<ro> element 410. The RO can be generated in eXtensible Markup Language(XML).

Referring to FIG. 4, the <ro> element 410 can include an Identifier (ID)field 412 having a device ID, a first encryption key field 414 having anencrypted CEK (E(CEK)), a second encryption key field 416 having anencrypted Message Authentication Code (MAC) key and an encrypted RightsObject Encryption Key (REK) (E(MAC, REK)), and an other informationfield 418 having other information.

The RO is encrypted with the REK being a symmetric key. Hence, a usercan acquire the CEK and access the digital contents only if the user hasthe REK.

The <mac> Element 420 may include a signature value of the <ro> element410 signed with the MAC key, which is encrypted and inserted in thesecond encryption key field 416.

FIG. 5 illustrates a device for generating, transmitting, and/orreceiving an RO according to an exemplary embodiment of the presentinvention.

In accordance with the exemplary embodiment of the present invention, adevice 500 includes a user input portion 510, a controller 520, acommunication module 530, and storage 540.

The user input portion 510 can be a user interface device, such as analpha-numeric keypad or QWERTY-style keyboard, either type using forexample physical buttons or a touch-screen, for receiving inputsincluding a password from a user. The controller 520 provides overallcontrol of the operations of the device 500, including data input/outputbetween components of the device 500. The communication module 530 mayinclude an interface for communicating with an external device, such asa wired/wireless Internet, Bluetooth, Universal Serial Bus (USB), orIrDA communication interface. The storage 540 can store programs usedfor the operations of the device 500 or various pieces of informationincluding content, for example, multimedia content.

Operation of the device 500 as a first device that generates andtransmits an RO will first be described below.

Upon receipt of a password from the user, the device 500 can generate apassword key of a predetermined length by encrypting the password andgenerate an RO using the password key. As described above,password-based encryption method of PKCS #5 or another method can beused for the password key generation.

The controller 520 can generate an REK for encrypting a CEK, and a MACkey for verifying the integrity of the RO. Also, the controller 520 canencrypt the CEK using the REK and encrypt the REK and the MAC key usingthe password key.

For content originally or previously associated with an RO received froman RI, the CEK can be a CEK included in the RO received from the RI. Onthe other hand, if the RO-transmitting device generates the contents, itcan also generate the CEK for content encryption.

The controller 520 can generate an RO using the encrypted CEK (E(CEK))and the encrypted MAC key and REK (E(MAC, REK)). Specifically, thecontroller 520 can generate an RO that includes an <ro> element with anID field having a device ID inserted, a first encryption key fieldhaving an encrypted CEK (E(CEK)), a second encryption key field havingan encrypted MAC key and an encrypted REK (E(MAC, REK)), and a <mac>element that is signed with the MAC key.

The controller 520 controls the communication module 530 to transmit theRO to another device that can share the user-entered password.

Now operation of the device 500 as a second device for receiving an ROwill be described.

The RO-receiving device 500 first stores a password shared with orreceived from another device that transmits an RO. The password may bestored in the storage 540 of the device 500.

Upon receipt of the RO from another device in the communication module530, the controller 520 generates the password key of a predeterminedlength by encrypting the stored password and interprets the RO using thepassword key.

The controller 520 decrypts the encrypted MAC key and the encrypted REK(E(MAC, REK)) included in the RO using the password key. The controller520 decrypts the encrypted CEK (E(CEK)) included in the RO using thedecrypted REK. Further, the controller 520 can verify the integrity ofthe RO by checking a signature value included in the <mac> element ofthe RO using the decrypted MAC key.

The controller 520 can also recover content by decrypting the contentusing the decrypted CEK. The recovered content can be used or output,for example, through an output device (not shown) such as a speaker or adisplay of the device, or a speaker or display connected to the device.

FIG. 6 is a flowchart illustrating a method for generating andtransmitting an RO according to an exemplary embodiment of the presentinvention.

To generate and transmit an RO, a device generates a password key byencrypting a password in step S610, and creates an RO using the passwordkey in step S620. The RO can then be transmitted to another device instep S630. The password can be shared between the RO-transmitting deviceand the RO-receiving device in this step or before this step, such aseven before the password-generating step of S610.

In accordance with the exemplary embodiment of the present invention,the RO can be generated in the procedure illustrated in FIG. 7.

FIG. 7 is a flowchart illustrating a method for generating an ROaccording to an exemplary embodiment of the present invention.

To generate the RO, the device generates an REK for encrypting a CEK,and a MAC key for verifying the integrity of the RO in step S622. Instep S624, the device encrypts the CEK using the REK.

For content associated with an RO received from an RI, the CEK can be aCEK included in the received RO in step S624. On the other hand, if theRO-transmitting device generates the content or receives the contentwithout DRM from a third device, the RO generation step S620 may includegenerating the CEK. Herein, the device can generate the CEK.

In step S626, the device encrypts the REK and the MAC key using thepassword key. As described above, the password key may be generated atstep S610. The device can generate the RO using the encrypted CEK(E(CEK)) and the encrypted REK and MAC key (E(MAC, REK)) in step S628.In this step, the RO may also include an ID field and a <mac> element.

FIG. 8 is a flowchart illustrating a method for receiving an ROaccording to an exemplary embodiment of the present invention.

A device receives an RO from another device in step S810 and generates apassword key of a predetermined length by encrypting a password in stepS820. The password may be shared with the RO-transmitting device in stepS810, or may be shared between devices at some point before step S810,such as through a registration step that may occur between devices. Instep S830, the device interprets the RO using the password key.

The RO interpretation can be carried out according to the procedureillustrated in FIG. 9.

FIG. 9 is a flowchart illustrating a method for interpreting an ROaccording to an exemplary embodiment of the present invention.

To interpret the RO, the device receiving the RO first decrypts theencrypted MAC key and REK (E(MAC, REK)) included in the RO using thepassword key in step S832. Then, the device decrypts the encrypted CEK(E(CEK)) included in the RO using the decrypted REK in step S834. Instep S836, the device verifies the integrity of the RO using thedecrypted MAC key.

The device can also decrypt content using the decrypted CEK.

As described above, a device can generate and transmit an RO to anotherdevice. Therefore, for content received from an RI, a device that isallowed to generate and transmit an RO can transmit the RO to anotherdevice by using a shared password as a password to encrypt and decryptthe RO. This way, the receiving device can receive content from thetransmitting device and also use the content without having to firstperform direct communication with the RI.

For content generated by the device, the device can transmit the contentto another device by using a shared password as a password to encryptand decrypt the RO, without having to first register the content to acontent management server, so that the receiving device can access anduse the content. Therefore, contents can be transmitted and receivedmore freely between devices that share a password, with better securityto protect the content.

The above-mentioned method according to the present invention may bestored in any form of recording media, such as CD-ROM, RAM, ROM, floppydisk, hard disk, or magneto-optical disk, or in any computer-readableform, such as computer code organized into executable programs, and themethod stored as a program in such recording media may be executed byany sort of computer or device including a processor and a readablememory.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method for generating a Rights Object (RO), comprising: generatinga password key by encrypting a password; and generating the RO using thepassword key.
 2. The method of claim 1, wherein generating the ROcomprises: generating a Rights Object Encryption Key (REK) forencrypting a Content Encryption Key (CEK), and generating a MessageAuthentication Code (MAC) key for verifying integrity of the RO;encrypting the CEK using the REK; and encrypting the REK and the MAC keyusing the password key.
 3. The method of claim 2, wherein if the RO isfor content associated with a received RO, the received RO beingreceived from a Rights Issuer (RI), the CEK is a CEK included in thereceived RO.
 4. The method of claim 2, further comprising generating theCEK for encrypting content associated with the RO.
 5. The method ofclaim 2, wherein the RO comprises an <ro> element and a <mac> elementsigned with the MAC key, the <ro> element comprising an Identifier (ID)field with a device ID, a first encryption key field comprising theencrypted CEK, and a second encryption key field comprising theencrypted MAC key and the encrypted REK.
 6. A device to generate aRights Object (RO), comprising: a user input portion to receive apassword; and a controller to generate a password key by encrypting thepassword, and to generate the RO using the password key.
 7. The deviceof claim 6, wherein the controller generates a Rights Object EncryptionKey (REK) for encrypting a Content Encryption Key (CEK), generates aMessage Authentication Code (MAC) key for verifying the integrity of theRO, encrypts the CEK using the REK, and encrypts the REK and the MAC keyusing the password key.
 8. The device of claim 7, wherein if the RO isfor content associated with a received RO, the received RO beingreceived by the device from a Rights Issuer (RI), the CEK is a CEKincluded in the received RO.
 9. The device of claim 7, wherein thecontroller generates the CEK for encrypting content associated with theRO.
 10. The device of claim 7, wherein the RO comprises an <ro> elementand a <mac> element signed with the MAC key, the <ro> element comprisingan Identifier (ID) field with a device ID, a first encryption key fieldcomprising the encrypted CEK, and a second encryption key fieldcomprising the encrypted MAC key and the encrypted REK.
 11. A method fortransmitting a Rights Object (RO), comprising: generating a password keyby encrypting a password; generating the RO using the password key; andtransmitting the RO from a first device to a second device.
 12. Themethod of claim 11, wherein the password is shared between the firstdevice and the second device.
 13. The method of claim 11, whereingenerating the RO comprises: generating a Rights Object Encryption Key(REK) for encrypting a Content Encryption Key (CEK), and generating aMessage Authentication Code (MAC) key for verifying the integrity of theRO; encrypting the CEK using the REK; and encrypting the REK and the MACkey using the password key.
 14. The method of claim 13, wherein if theRO is for content associated with a received RO, the received RO beingreceived from a Rights Issuer (RI), the CEK is a CEK included in thereceived RO.
 15. The method of claim 13, wherein the method furthercomprises generating the CEK for encrypting content associated with theRO.
 16. The method of claim 13, wherein the RO comprises an <ro> elementand a <mac> element signed with the MAC key, the <ro> element comprisingan Identifier (ID) field with a device ID, a first encryption key fieldcomprising the encrypted CEK, and a second encryption key fieldcomprising the encrypted MAC key and the encrypted REK.
 17. The methodof claim 11, wherein generating the password key comprises generatingthe password key using a password-based encryption method of Public-KeyCryptography Standard (PKCS) #5.
 18. A device to generate a RightsObject (RO), comprising: a user input portion to receive a password; acontroller to generate a password key by encrypting the password, and togenerate the RO using the password key; and a communication module totransmit the RO from the device to a receiving device.
 19. The device ofclaim 18, wherein the password is shared between the device and thereceiving device.
 20. The device of claim 18, wherein the controllergenerates a Rights Object Encryption Key (REK) for encrypting a ContentEncryption Key (CEK), generates a Message Authentication Code (MAC) keyfor verifying the integrity of the RO, encrypts the CEK using the REK,and encrypts the REK and the MAC key using the password key.
 21. Thedevice of claim 20, wherein if the RO is for content associated with areceived RO, the received RO being received by the device from a RightsIssuer (RI), the CEK is a CEK included in the received RO.
 22. Thedevice of claim 20, wherein the controller generates the CEK forencrypting content associated with the RO.
 23. The device of claim 20,wherein the RO comprises an <ro> element and a <mac> element signed withthe MAC key, the <ro> element comprising an Identifier (ID) field with adevice ID, a first encryption key field comprising the encrypted CEK,and a second encryption key field comprising the encrypted MAC key andthe encrypted REK.
 24. The device of claim 18, wherein the controllergenerates the password key using a password-based encryption method ofPublic-Key Cryptography Standard (PKCS) #5.
 25. A method for receiving aRights Object (RO), comprising: receiving the RO at a first device froma second device; generating a password key by encrypting a passwordshared between the first device and the second device; and interpretingthe RO using the password key.
 26. The method of claim 25, whereininterpreting the RO comprises: decrypting an encrypted MessageAuthentication Code (MAC) key and an encrypted Rights Object EncryptionKey (REK) included in the RO using the password key; decrypting anencrypted Content Encryption Key (CEK) included in the RO using thedecrypted REK; and verifying integrity of the RO using the decrypted MACkey.
 27. The method of claim 26, further comprising: decrypting contentassociated with the RO using the decrypted CEK.
 28. The method of claim25, wherein generating the password key comprises generating thepassword key using a password-based encryption method of Public-KeyCryptography Standard (PKCS) #5.
 29. A device to receive a Rights Object(RO), comprising: a communication module to receive the RO from atransmitting device; a storage to store a password shared with thetransmitting device; and a controller to generate a password key byencrypting the password, and to interpret the RO using the password key.30. The device of claim 29, wherein the controller decrypts an encryptedMessage Authentication Code (MAC) key and an encrypted Rights ObjectEncryption Key (REK) included in the RO using the password key, decryptsan encrypted Content Encryption Key (CEK) included in the RO using thedecrypted REK, and verifies integrity of the RO using the decrypted MACkey.
 31. The device of claim 30, wherein the controller decrypts contentassociated with the RO using the decrypted CEK.
 32. The device of claim29, wherein the controller generates the password key using apassword-based encryption method of Public-Key Cryptography Standard(PKCS) #5.